title: Ultra-fast steady state free precession and its application to in vivo (1)H morphological and functional lung imaging at 1.5 tesla.
abstract: OBJECTIVE
  The speed limit for three-dimensional Fourier-encoded steady state free precession (SSFP) imaging is explored on a clinical whole body system and pushed toward a pulse repetition time (TR) close to or even below the 1 ms regime; in the following referred to as ultra-fast SSFP imaging.
  
  
  METHODS
  To this end, contemporary optimization strategies, such as efficient gradient switching patterns, partial echoes, ramp sampling techniques, and a target-related design of excitation pulses were applied to explore the lower boundaries in TR for SSFP-based Cartesian imaging.
  
  
  RESULTS
  Generally, minimal TR was limited in vivo by peripheral nerve stimulation, allowing a TR ∼1 ms for isotropic resolutions down to about 2 mm. As a result, ultra-fast balanced SSFP provides artifact-free images even for targets with severe susceptibility variations, and native high-resolution structural and functional in vivo (1)H imaging of the human lung is demonstrated at 1.5 T.
  
  
  CONCLUSIONS
  On clinical whole body MRI systems, the TR of SSFP-based Cartesian imaging can be pushed toward the 1 ms regime. As a result, ultra-fast SSFP protocols might represent a promising new powerful approach for SSFP-based imaging, not only for lung but also in a variety of clinical and scientific applications.
authors.affiliation: Division of Radiological Physics, Department of Radiology, University of Basel Hospital, Basel, Switzerland.
authors.forename: Oliver
authors.initials: O
authors.lastname: Bieri
mesh_terms: D006801:Humans; D008168:Lung / Q000033:anatomy & histology / Q000502:physiology; D008279:Magnetic Resonance Imaging / Q000379:methods*
keywords: SSFP; imaging; lung; steady state; ultra‐fast